Snorkel shows partial credit in RL can oppose completion, proposes binary-gated GRPO

ajratner · x · 2026-10-16

Snorkel AI researchers show that partial-credit rewards in agent RL can work against the goal they serve: a policy that always makes partial progress but never finishes (pass@k = 0) can score a higher fractional return (0.50) than one that completes 20% of the time. Naive partial credit teaches models to satisfy easy checks while abandoning the path that satisfies them all, and blending it with pass/fail doesn't fix this unless nearly all weight sits on pass/fail. They introduce binary-gated GRPO, which removes the conflict while keeping partial credit's benefits; with it, harm requires a specific combination of conditions rare in natural settings.

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